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    <h1>Reduce 实现promise 的队列</h1>

    <script>
      function query(num) {
        num.reduce((promise, n) => {
          return promise.then((_) => {
            return new Promise((resolve) => {
              setTimeout(() => {
                console.log(n)
                resolve()
              }, 1000)
            })
          })
        }, Promise.resolve())
      }
      query([1, 2, 3, 4, 5, 6, 7, 8, 9])
    </script>
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